my 96 e300's center ac vents are blowing warm and cold air at the same time even with the acc temperature settings of low.for some reason the left center vent is blowing warmer air than the right one. i repeat warm not hot air. it is not unbearable but it is uncomfortable especially after sitting for a while in a hot florida day.
has anyone encountered this problem ?
can anyone direct me on how to diagnose this? a/c systems is something that is new to me.
thanks

Most likely cause: low refrigerant level.
Possible cause: plugged dryer.
Possible cause: bad duovalve.

Because a restriction or a duovalve can also cause this, I do not recommend blindly adding refrigerant.

thanks matt, sorry for the dumb question-but what is a duovalve, what does it do and where is it located?

Older (and "lower class") models have a monovalve that controls the flow of coolant to the heater core; later models (S-class got them first, of course) have a "duovalve, a double valve that allows driver and front seat passenger to have individual control of the hot coolant to control the temperature on their side of the car. One half of the duovalve handles the driver side and the other half controls the passenger side. If one side fails (open, closed, or stuck in the middle) then that part of the climate control system won't work correctly.

The Mercedes climate control system is sufficiently complicated that you sometimes have a hard time determining what has gone wrong. However, the 210 came with built-in diagnostic codes that you can read by pressing buttons on the control panel. The procedure is posted somewhere on this forum or another but I don't remember just now where it is or whether it will detect a bad duovalve. Maybe someone else will point you in the right direction.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

To eliminate the duovalve as the problem, block off the water flow in the pipe from the duovalve to the engine.

Its located in the same firewall compartment as the computer box on the pass side of the engine compartment.

Find an 8 or 12" screwdriver and give it a few good whacks with the handle before doing much else to it.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Still trying to diagnose why my 96 e300's center vents are blowing warm and cold-pulled out some numbers from the ccu and here is what i have
1-42
2-54
3-21
4-22
5-28
6-90
7-13
8-52

error codes are :e61-462,e61-232,e61-234,e61-413,e61-462,e61-422,e61-424 and e-fr
does anyone know what these codes mean?
thanks for all the help

I not sure if yours is reporting in C or F? Was it 54F or 54C (129f) outside when you did this? If it was 54f, you need to have the engine running (and have it at opt temp) when you pull the data and codes and repost them.

Here's the code list. http://www.continentalimports.com/ser_ic40142.html
http://www.continentalimports.com/ser_ic40142a.html

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

thanks terry,
it was 54F. i had the engine on for about 10 mins when i pulled these numbers

The duovalve is the heater control valve. It sits next to the module box under the hood (LHD cars). Three hoses meet at the valve. Block off the front pipe, the one that goes to the engine. This will disable the heater entirely.

With the heater disabled, if there is a difference in vent temperatures, the AC is at fault.

However, if you measure the temperature before the engine warms up, you'll approximate a disabled heater.

If the AC is at fault, confirm the refrigerant level before going on. If it's low and recharging to spec fixes it, you've found the trouble.

guys:
just redid my readout as terry suggested-outside temp according to the instrument panel is 86F, engine temperature per the temp gauge is around 95F
results are:
1-24(this boggles me converted to F around 75.2)on my first post the reading was 54 if it is converted to F it is 129! as terry noted
2-43
3-18
4-13
5-13
6-98
7-10
8-44
error codes-e61462,e61232,e61234,e61413.e61422.e61424 and e fr(or it could be ef f) as the pixels are fading
any ideas?